20种氨基酸 ALIPHATIC AMINO AC IDS CH CH2一CH COO H H3N-C-CO0 H3N-C-COO 00 H H H H Glycine(Gly)G Alanine(Ala)A valine(val)v Leucine(Leu)L Isoleucine(le)I AMINO ACIDS WITH HYDROXYL-OR SULFUR-CONTAINING SIDE CHAINS CH3 CYCL IC AMINO ACID H SH CH HCOH CH2● H.CH H -COO H.- COO H3N-C-COO H2N一C-c00 HN一C-c00 H Serine(Ser)S Cysteine(Cys)C Threonine(Thr)T Methionine(Met)M Proline(PrO)P20种氨基酸